G. THE RECTUM, BY E. VERSON. 



581 



angles. A few millimeters higher a few fibres of the posterior 

 portion of the longitudinal muscular layer mutually inter- 

 penetrate with those of the musculi recto-coccygei, which, pro- 

 ceeding from the sacrum, here terminate. 



Three distinct portions of the musculus levator ani can be 

 distinguished, each of which differs in the nature of its fibres 

 from the other, the innermost being formed of organic, the 

 middle of a mixture of organic and transversely striated, and 

 the external (which constitutes the largest portion) of purely 



Fig. 111. 



Fig. 111. Longitudinal section of the musculature of the rectum. 



animal fibres. It is only the innermost of these three groups 

 which enters into immediate relation with the rectum, its 

 constituent fibres in part penetrating obliquely into the longi- 

 tudinal muscular layers, and interweaving with them both in 

 an upward and downward direction, and in part crossing them 

 at right angles, and blending with the circular muscular layer. 

 At the level of the sphincter internus the longitudinal fibrous 

 layer becomes separated to some extent from the former, whilst 

 fasciculi of connective tissue intervene between them ; and the 



